This invention relates generally to the field of humidity control devices, and more specifically to humidistat controllers having a humidity sensor mounted into a furnace duct.
In the past, a common approach to humidity control within residential and commercial buildings has been to install a humidistat to sense and control the ambient humidity within an enclosed space. These humidistats were commonly designed to sense the temperature and/or relative humidity within the enclosed space and then provide control to a usually remote device, which would operate to humidify or dehumidify the room air. Traditionally, these humidistats were mounted either on a wall in a common living area, or on a furnace duct or plenum.
Although a conventional wall mounted humidistat is readily accessible to the occupants for proper adjustment of the humidity level, it often results in significant installation problems due to the type of wall construction. Additionally, since the humidistat is commonly configured to monitor temperature and relative humidity, there may be instances where the sensed humidity may not be an accurate representation of the humidity throughout the building. This may then result in an improper adjustment of the humidity level.
Placement of the humidistat on the duct or plenum of a furnace has the initial advantage of allowing the humidity-sensing element to be in contact with the return air from the building. This allows humidity or temperature sensing elements within the humidistat to obtain an average relative humidity and temperature of the entire living space. Likewise, placement near the furnace typically involves shorter cable runs to any associated humidity controlling equipment, saving additional installation costs.
Prior commercial humidistats have generally included at least a relative humidity sensing element adapted to be partially enclosed within a housing, the housing including a wall or furnace-mountable base and front cover attached to the base. The bases of the prior commercial devices were generally planar and required a large rectangular cutout in the furnace duct to expose the sensing element to the return air. The humidity sensing element was often mounted to the front face of the housing, and a cover was attachable to the base via forwardly extending spring clips on the base ends, which latched over projections formed on the cover ends. One example of this type of humidistat may be found in U.S. Pat. No. 3,523,217.
Humidistats which are designed to place the humidity-sensing element within the return air furnace duct, unfortunately have a significant drawback. Due to the size and nature of the humidity control, large rectangular holes were required to be cut into the furnace duct or plenum to allow exposure of the humidity-sensing element to the duct airflow. These holes ranged in size, but were often two inches by four inches, which required the cutting to be performed with common sheet metal cutting tools. In a typical installation, the installer would create a hole in the ductwork (usually by means of a drill), and then further expand the hole to the correct size with sheet metal cutting snips. Furthermore, due to the large hole placed into the duct or plenum, building inspectors often require leaks around these rectangular cutouts to be sealed by caulking.
The Applicant's invention now described provides an improved humidistat mounting method and apparatus which allows sensor placement within a furnace duct with minimal damage to the duct.